PeriodontalLigament

The periodontal ligament (PDL) is a specialized connective tissue that surrounds the tooth root, occupying the narrow space between cementum and the alveolar bone surface. It anchors the tooth to the jaw while allowing micro-movements and absorbing occlusal forces. The normal width is approximately 0.2 to 0.4 mm and the PDL is dynamic, continually remodelled in response to function.

Composition. It is composed mainly of type I collagen fibers arranged into principal (Sharpey's) fibers that insert into cementum and bone, arranged in bundles oriented according to functional needs. The tissue contains fibroblasts, cementoblasts, osteoblast-like cells, undifferentiated mesenchymal cells, blood vessels, and nerve fibers within an extracellular matrix rich in proteoglycans and glycoproteins.

Functions. The PDL serves as a ligament that suspends the tooth in its socket, distributes and cushions occlusal loads, participates in tooth eruption and eruption remodeling, and houses mechanoreceptors that contribute to proprioception and bite force regulation. It also plays a central role in orthodontic tooth movement through controlled remodeling of the alveolar bone and ligament.

Vascular and nerve supply and development. Blood supply comes from periodontal vessels; innervation from branches of the trigeminal nerve. The PDL derives from the dental follicle and forms during tooth eruption; it can regenerate after injury but regeneration may be limited by disease or aging.

Clinical significance. In periodontal disease, PDL fibers break down leading to tooth mobility and bone loss; in orthodontics, the PDL mediates tooth movement through remodeling. Healing involves regeneration of collagen fibers, cementum, and bone; regenerative techniques aim to restore PDL function.